(function(doc,win){
    var docEl=doc.documentElement,
    resizeEvt='orientationchange' in window ? 'orientationchange':'resize',
    recalc = function(){
        var clientWidth = docEl.clientWidth;
        if(!clientWidth) return;
        docEl.style.fontSize = 100 * (clientWidth / 750) + 'px'
    };
    recalc()
    if(!doc.addEventListener) return;
    win.addEventListener(resizeEvt,recalc,false);
    doc.addEventListener('DOMContentLoaded',recalc,false)
})(document,window)